Quantum Numbers

My book here says that ' Despite the shielding of the outer electrons from the nucleus by the inner shell electrons, the attractive force experienced by the outer shell electrons increases with increase of nuclear charge. In other words, the energy of interaction between the nucleus and electron (that is orbital energy) decreases (that is more negative) with the increase of atomic number. '
Now i understood the first part. But whatever is said after 'in other words', i am not able to understand what is said here.
How is more attractive force synonymous to decrease of energy of interaction b/w nucleus and electron?

Yes, if your potential is more attractive you binding energy will decrease. You must keep in mind that the binding energy is negative, hence it's decrease it's actually associated with the increase of its magnitude.

Staff: Mentor

Potential energy is the stored energy in a system by virtue of its position. For example an apple sitting on a table has energy by virtue of the fact it is above the floor. Remove the table and it falls to the floor converting the potential energy to kinetic energy.

Binding energy is the energy required to dissemble a system into its constituent parts.